System for compensating jitter of video signal

Abstract

A horizontal synchronizing signal contained in a composite video signal undergoing a phase fluctuation is phase modulated and substituted for the original horizontal synchronizing signal. The phase modulation of the horizontal synchronizing signal of the input signal is effected at a phase modulation circuit and then the phase modulated signal is applied to an AFC circuit unit which has the same transfer characteristic as that of a horizontal AFC circuit of an ordinary television receiver set. The phase modulation circuit is controlled by a signal in response to a phase difference between the output of the AFC circuit unit and the original horizontal synchronizing signal. A composite video signal containing the horizontal synchronizing signal subjected to the phase modulation in this manner is applied to the television receiver set, thereby displaying a picture image free from the fluctuation.

We claim: 
     
       1. A system for suppressing a phase fluctuation of a composite video signal accompanied therewith comprising: means for extracting an original horizontal synchronizing signal from the input composite video signal;   means for phase modulating the original horizontal synchronizing signal extracted by said extracting means;   means including an AFC circuit unit having the same transfer characteristic as that of a horizontal AFC circuit of an ordinary television receiver set and adapted to control said phase modulating means by supplying an output signal from said phase modulating means to said AFC circuit unit, comparing in phase the output signal from said AFC circuit unit with the original horizontal synchronizing signal extracted from said extracting means and feeding back a resultant comparison signal to said phase modulating means; and   means substituting the original horizontal synchronizing signal contained in the composite video signal by the horizontal synchronizing signal subjected to the phase modulation at said phase modulating means to deliver out the phase modulated horizontal synchronizing signal.   
     
     
       2. A phase fluctuation suppressing system for suppressing a fluctuation of a picture image produced by displacing a composite video signal accompanied with a phase fluctuation on a video monitor comprising, means for extracting a video signal and a synchronizing signal from an input composite video signal by separating them;   means for phase modulating the separated synchronizing signal by a control signal applied externally;   an AFC circuit unit having the same transfer characteristic as that of an AFC circuit of a horizontal deflection circuit provided for an ordinary television receiver set and adapted to produce a signal synchronized with the horizontal synchronizing signal modulated by said phase modulating means;   means comparing in phase the signal delivered from said AFC circuit unit with the separated horizontal synchronizing signal and applying as a control signal a signal in response to a resultant phase difference to said phase modulating means; and   means adding the horizontal synchronizing signal subjected to the phase modulation at said phase modulating means to the video signal separated from the composite video signal at said extracting means and applying an added signal to the video monitor.   
     
     
       3. The phase fluctuation suppressing system according to claim 2 wherein a circuit differentiating the input signal and delivering out a differentiated output is added to said means for applying the control signal to said phase modulating means. 
     
     
       4. The phase fluctuation suppressing system according to claim 2 wherein a circuit integrating the input signal and delivering out an integrating output is added to said means for applying the control signal to said phase modulating means.